The metal silicon is used as a raw material in various applications based upon its purity. Regular grade silicon is nominally 99% pure silicon and hyperpure silicon is nominally 99.99% silicon. Hyperpure silicon is used extensively for the production of solid state devices and silicones. One method of producing crystalline silicon with purity up to hyperpure silicon is known as directional solidification. In this method a column of molten silicon with impurities is slowly cooled from the bottom upwards. With appropriate process parameters, crystalline silicon forms in the cooled region as most impurities remain in the molten portion of the mass. At the end of the process, the cooled mass is appropriately trimmed to remove outer regions of impurities and the crystalline silicon mass is further processed, for example, cut into thin wafers for use in the production of semiconductors. U.S. Pat. No. 6,136,091, U.S. Pat. No. 5,182,091, U.S. Pat. No. 4,243,471 and U.S. Pat. No. 4,218,418 disclose various methods of producing crystalline silicon by directional solidification.